Video programming may be distributed to a wide audience via various television systems, such as but not limited to, subscriber systems, satellite systems, direct broadcast satellite (DBS) and cable television (CATV) systems. Under certain contractual provisions, a specific programming event may be “blacked out” in certain geographic areas. For example, a sports event may be restricted to areas outside of the local market for ticket sales to the live event. Accordingly, many video programming delivery systems provide for geographic areas to be selectively blacked out for specific programming events.
Systems for controlling blacked out regions by geographic designation are well known. For example, U.S. Pat. No. 5,036,537 to Jeffers et al. describes a direct broadcast satellite system in which programming is distributed through a composite television signal which includes a plurality of levels of programming called tiers. Each tier carries a different variety of programming. A particular program may suit several tiers, much like a library index card listing having several possible topics of interest. Thus, a particular program may appear on one or more tiers.
Certain programs, whether paid for by subscription or on a pay-per-view basis, may be considered by the subscriber as inappropriate for viewing by the household or certain members thereof. Accordingly, the satellite system may incorporate a means for blocking out the tiers on which such programs are distributed so that they cannot be decoded and displayed by the subscriber's receiver unit. The system may also black out programming in a particular geographic area, for example, as mentioned above, certain sporting events such as baseball games, football games, boxing matches, and the like.
In the direct broadcast satellite system of U.S. Pat. No. 5,036,537, each receiver unit is provided with a memory for storage of a designation code representing its geographic location, and a memory for storage of indications of tiers upon which programs to be blacked out are to be distributed. After each receiver unit is provided with a designation code, the receiver units are globally addressed. Each receiver unit having a selected designation code stored therein is provided with a blackout tier indication for storage. When a program is selected for viewing, the receiver unit compares the program tier indication distributed with the program and the stored blackout tier indication. If the indications match, the selected program cannot be displayed.
In a related tier authorization scheme, U.S. Pat. No. 4,685,131 to Home describes a program blocking method for use in direct broadcast satellite systems. Programming tiers are authorized for viewing on an impulse pay-per-view basis. A system operator controls individual receiver units to block the display of programming on selected tiers, e.g., blacked out sporting events, or objectionable content. The broadcast signal includes portions addressable to particular receiver units. These portions include a designation of tiers to be blocked and a command to store the designation of the tiers in the unit memory. Upon a command to display a program on a selected tier, the memory is accessed and the stored designation is compared with the selected tier. Receivers having stored designations corresponding to the selected tier are unable to display the program.
In yet another tier authorization scheme, U.S. Pat. No. 4,864,615 to Bennett et al. describes a system that may be used to collect subscribers into a blackout group which is assigned to a unique authorization tier. When a program or event begins, those descramblers that do not possess the proper authorization tier are prevented from decoding the received television signal and will therefore be blacked out for the program or event.
U.S. Pat. No. 6,292,568 to Akins, III et al. describes a cable television system that provides conditional access to services. The cable television system includes a headend from which service “instances”, or programs, are broadcast, and a plurality of set top units for receiving the instances and selectively decrypting the instances for display to system subscribers. The service instances are encrypted using public and/or private keys provided by service providers or central authorization agents.
In the system of U.S. Pat. No. 6,292,568, blackout/spotlight information may be provided, which defines a geographic area which is to be blacked out or spotlighted by an instance of a service. The system uses coordinates to define a point in a geographical coordinate system defined by an entitlement agent or by an entitlement control message (ECM), and a blackout radius that is used to determine a region that is centered about the defined point. For example, if the blackout field of the ECM indicates that a blackout applies to the service, then the blackout information is used to determine whether the location specified by the position coordinates is within the blacked out region; if so, the system does not decrypt the control words and viewing is blocked.
In the event that a television broadcast is blacked out, it may be desired to provide alternative programming to the television subscribers during the blacked out event. For example, a CATV operator may manually switch to another available signal for the blacked out event. As another example, a program provider of the blacked out event may offer alternative programming from another satellite feed during the blackout. The CATV operator sends personnel to the headend site of the CATV system to connect another satellite receiver or retune the original satellite receiver to the alternate satellite feed during the blackout. Following the blackout, the original satellite receiver may be re-connected or manually tuned back to the primary satellite feed.
In addition to such manual switching arrangements, automatic switching or retuning of satellite receivers during a blackout is also known. U.S. Pat. No. 5,235,643 to Anderson et al. describes a remotely retunable receiver for use in a satellite video programming distribution system, which includes the capability to retune groups of subscribers to different satellite feeds during a blackout of a video programming event. To achieve flexible control over program blackouts, a receiver retune command message is selectively sent to desired groups of descramblers at CATV satellite downlinks. The retune command message identifies an alternate satellite feed and a time for which the satellite receiver is to tune to the alternate satellite feed. The receiver stores the retune command, and at the appropriate time retunes the satellite receiver to the identified alternate feed.
Conditional access mechanisms for providing access only to authorized users of content are well-known in the art; many such mechanisms include use of a removable security element such as a smart card. One attempt to provide such effective mechanisms is described in U.S. Pat. Nos. 5,282,249 and 5,481,609, both to Cohen et al. The disclosed system enables a signal containing media content to be broadcast widely, yet only to be played back or otherwise displayed by authorized users. This signal could contain a television program, for example. The signal is scrambled, such that the authorized users are able to unscramble the signal and play back or otherwise display the media content only with the proper security device, such as a smart card for example. Thus, widely received media content is still protected from access by unauthorized users.
Scrambled television data streams described in the Cohen et al. patents comprise both scrambled data representing television signals and coded control messages, also known as ECMs (Entitlement Control Messages). The ECMs of Cohen et al. comprise, in a coded form, data necessary for generating a control word (CW) which may be used to descramble the scrambled data representing television signals.
Data necessary for generating a control word is known in the background art to take many different forms and may include, in general, at least any of the following: a control word; an encrypted control word packet which is intended to be decrypted before use; and a seed to a generating function such as, for example, a one-way function which generates the control word upon input of the seed. Throughout the present specification and claims the terms “control word generating information” and “CW generating information” are used interchangeably to designate data necessary for generating a control word in any appropriate form, as described above.
Another attempted solution is described in published European Patent Application No. EP 0858184 and in corresponding U.S. Pat. No. 6,178,242, which disclose a digital recording protection system. The disclosed system enables the digital content to be sent in a digitally scrambled format, such that the digital content cannot be read and/or displayed without a key. The key is obtained from a control message, which is only sent to authorized users. Preferably, the key is obtained from coded information contained within the Entitlement Control Message, or ECM, for generating a control word associated with the ECM. Thus, only authorized users are able to correctly read and/or display the digital content.
In addition, the system and method described in European Patent Application No. EP 0858184 enable the authorized user to record and playback or otherwise display the digital content, while preventing the user from producing and distributing multiple playable copies of the digital content to other, non-authorized users. Therefore, the authorized user is able to fully use and enjoy the digital content, while the content itself is still protected from unauthorized use.
Personal video recorders (PVRs), which allow digital recording of broadcast or otherwise transmitted information such as television programs, are well known in the art. Salient features of one such system are described in published PCT Patent Applications WO 00/01149 and WO 01/52541, both assigned to NDS Limited.
The disclosures of all references mentioned above and throughout the present specification are hereby incorporated herein by reference.